Is the sun shrinking?

Part Two: The debate continues

Editor’s note: As Creation magazine has been continuously published since 1978, we
are publishing some of the articles from the archives for historical interest, such as this. For teaching and
sharing purposes, readers are advised to supplement these historic articles with more up-to-date ones suggested in the Related Articles below.

Editors’ note, March 2014: This series was based on the scientific information available at the time of writing, which suggested that the sun was shrinking. Thus it supported the idea that much of the sun’s energy was generated by gravitational collapse, whereas there were much fewer neutrinos than what would be expected if the sun was mainly powered by nuclear fusion. This information would limit the sun’s age to much less than the evolutionary 4.5 billion years.

However, since then, the missing neutrinos were found. Thus fusion, not gravitational collapse, is the source of the sun’s power. However, this suggests another limit to the sun’s age: fusion would contract the sun’s core, making the fusion reactions stronger, so the sun would become brighter with age. But this would imply a much cooler sun billions of years ago. This is the ‘faint young sun paradox’—a problem for long ages.

This all shows the need to keep up to date with science, and even more importantly, shows that scientific models and evidence are always tentative. Thus they should never be placed on the same level as the God-breathed Scripture, which never becomes out-of-date. Indeed, this was pointed out by an editorial written at the same time as the shrinking sun articles, ‘Hanging Loose’.

In 1979, scientists Eddy and Boornazian cautiously announced that their studies
of solar measurement records from Greenwich Observatory in England, and the US Naval
Observatory in Washington, conclusively showed that the sun was shrinking. Its diameter
was decreasing at a rate of almost six feet per hour.1

There were potentially astounding implications. The announcement by Eddy and Boornazian
with respect to the age of the sun (and hence the solar system), along with the
apparent conflict with previously held ideas about how the sun produces its heat
and light, did not go unnoticed. A vigorous healthy debate among solar astronomers
began.

After their own analyses of the Greenwich and Washington data, plus comparisons
of solar eclipse records, and consideration of photographic and other relevant evidence,
many colleagues agreed with Eddy and Boornazian but the consensus seemed to be that
the shrinkage rate was less than half that initially suggested.

Mercury transit data

However, not all scientists agreed that the evidence indicated the sun is shrinking.
A number disputed the reported figures and presented results of their own that seemed
to indicate no shrinkage. Among them was Irwin Shapiro of the Massachusetts Institute
of Technology. He reported a series of figures for the sun’s diameter that
he had calculated from studies of transits of the planet Mercury.

For more than two centuries astronomers had been studying the exact orbit of Mercury.
Occasionally Mercury passes directly between the earth and the sun, so that it crosses
our direct line of sight to the sun. Viewed from earth, Mercury appears to cross
the face of the sun from one side to the other, and this is called a transit.

Irwin Shapiro had collected a whole series of records of observations of the transit
of Mercury. He realized that if he put into his computer the time at which the transit
started, and the time at which the transit finished, he could use these records
as a series of measurements of the sun’s diameter. If the sun’s diameter
had been larger in the past, then the transit time of Mercury should have been longer
then than it is today.

So he analysed his collection of data. He concluded that the records from 23 transits
of Mercury between 1736 and 1973 indicated that there had not been any
statistically significant change in the sun’s diameter over those 237 years.
He reported his findings in the journal Science in April 1980.2

But a closer look at Shapiro’s results, and when statistical error margins
were applied to each of his data points, then it was clear that Shapiro’s
analysis of the transit of Mercury data could not definitely rule out the possibility
that there was some shrinkage of the sun. All Shapiro could really say was that
he couldn’t detect any shrinkage if shrinkage was indeed occurring.
Yet while his results showed no indication of any significant change in the diameter
of the sun, his regression analysis yielded a decrease in solar diameter of under
0.2 second of arc per century at a confidence limit of >90%. Thus it could easily
be argued that Shapiro’s results are still comparable with Dunham et al.’s
approximate 0.2 second of arc per century shrinkage rate based on records of the
1715 and 1979 solar eclipses,3 and
Howard’s 0.5 second of arc per century shrinkage rate from 50 years (1930–1980)
of solar photography.4

No shrinkage?

But three English scientists, Parkinson, Morrison and Stephenson also looked at
the Greenwich data and their own set of Mercury transit data as well as the solar
eclipse data, and they too came to the conclusion that there was no detectable shrinkage
of the sun during the past 250 years.5
However, they suggested that there is some evidence for the occurrence of periodic
changes in the sun’s diameter of about 0.02% on a time-scale of 80 years.
They also felt that Eddy and Boornazian’s findings were the result of instrumental
and observational defects (they outlined these in detail) rather than real changes.

Next to join the fray was German scientist Wittmann, who pointed out that the distinguished
eighteenth century astronomer, Tobias Mayer, had made a series of highly reliable
observations of the sun between 1756 and 1760. Wittmann proceeded to analyse Mayer’s
129 transit observations and declared that there was excellent agreement with more
recent photoelectric transit observations, thus lending no support whatsoever to
claims that the sun is shrinking.6

A critical reassessment

Subsequently, in a valiant effort to decisively resolve this debate over whether
the sun is shrinking or not, Ronald Gilliland undertook a comprehensive reassessment
of all the five data sets of apparent solar diameter measurements published by the
authors participating in the debate. His results end conclusions were published
in The Astrophysical Journal of the American Astronomical Society in September
1981.7 In his summary, Gilliland reported
that his analysis of the five different data sets, including the meridian circle
(Greenwhich and Washington) observations, the timings of transits of Mercury, and
the durations of total solar eclipses, consistently suggested the presence of a
76-year modulation (cycle of variation) of the solar radius. He further suggested
that the last solar radius maximum occurred in 1911, and that the half-amplitude
of variation (half the change in radius between the minimum and maximum of the cycle)
is approximately 0.2 second of arc per century or 0.02% of the solar radius.

Interestingly, Gilliland was also mildly critical of some of his colleagues’
handling of the data. For example, he pointed out that in his analysis he had not
thrown out portions of the Greenwich data as suggested by Parkinson, Morrison and
Stephenson to account for possible systematic errors resulting from instrumental
and observational changes. He reasoned that to remove certain sections of the data
set which showed discontinuities correlated with instrumental changes tended to
introduce further biases into the data sat. He concluded that the reader should
be warned of uncertainties which exist in the individual data sets as Parkinson,
Morrison, and Stephenson had done, but subjective removal of certain sections to
support the Parkinson et al. premise that the solar diameter has been constant
over the past 250 years should also be viewed with caution.

In deriving his results, Gilliland commented that the remarkable agreement between
independent data sets and combinations of sets in predicting the maximum twentieth
century radius near l910 with a cycle time of about 76 years is the strongest evidence
supporting a cyclic solar radius change. Furthermore, the most noticeable feature
common to all five data sets is a decrease in solar radius from l910 to the 1940s.
He noted that without exception the analyses show this twentieth century feature.
The fact that this cyclicity is clearly evident in both the Greenwich and Washington
observations lends support to his contention that these series of measurements still
have some validity despite Parkinson, Morrison and Stephenson’s attempt to
downplay their significance due to claimed instrumental and observational defects.

Some shrinkage still

Gilliland was also bold enough to admit that since stellar evolution theory predicts
that the sun should increase in size with increasing age (i.e. the sun’s diameter
should be increasing), any decrease is quite significant. To be sure, he said, the
discrepancies between independent data sets—for example, a clear long-term
decreasing trend in the Greenwich measurements reported by Eddy and Boornazian in
1979 and the lack of a trend in the Mercury transit data of Shapiro (1980)—makes
simple interpretations problematic. But Gilliland maintained that in the partially
justified, but perhaps overzealous criticism of the early Eddy and Boornazian claims
there is the distinct possibility that much smaller but still fundamentally important
long-term trends were being inadvertently disclaimed. He then noted, as we have
already done above, that the equatorial trend derived from Mercury transits by Parkinson,
Morrison and Stephenson over the interval 1723–1973 precisely agrees with
the polar radius decrease of almost 0.2 second of arc per century over the interval
1715–1979 derived from observations of total solar eclipse path widths by
Dunham et al.

Even more telling is the fact that even though Parkinson, Morrison and Stephenson
argued that the horizontal Greenwich measurements were not reliable before 1854
or after 1915 because of instrumental and observational inadequacies, analyzing
only the horizontal Greenwich data from 1854–1914 yields a long-term decrease
trend of just over 0.3 second of arc per century. Thus Gilliland claimed that the
objective result from the Parkinson, Morrison and Stephenson (1980) paper should
have been that the Mercury transit data support a long-term radius decrease of over
0.1 second of arc per century and that the most reliable portions of the Greenwich
observations support a somewhat steeper decrease.

To quote Gilliland:

Given the many problems with the data sets, one is not inexorably led to
the conclusion that a negative secular (long-term) solar radius trend has existed
since AD 1700, but the preponderance of current evidence indicates that such is
likely to be the case.

Furthermore, even

with allowance for possible systematic errors in both the meridian circle
and Mercury transit timing observations, a negative secular (long-term) trend of
solar radius is still supported.

Steady long-term decrease

Thus we can conclude that a thorough analysis of all the available evidence clearly
suggests a steady long-term decrease of the solar diameter (i.e. the sun is shrinking)
at a rate of almost 0.2 second of arc (150 kilometers or 93 miles) per century or
approximately 30 centimeters (less than one foot) per hour, superimposed upon a
76–80 year cycle of systematic increase and decrease over a range of 0.8 second
of arc (600 km or 373 miles).

Oscillations and eclipses

But Gilliland’s thorough analysis of the data and definitive conclusion have
far from settled the debate. Not unexpectedly, both Stephenson and Parkinson responded
to Gilliland’s reanalysis of the available data. Stephenson reported in Scientific
American8
that his reanalysis (with the help of his colleagues) of the thirty transits of
Mercury and six total solar eclipses between 1715 and 1979 had indicated only a
negligible change in the sun’s diameter, calculated as a decrease of 0.16
Â± 0.14 second of arc per century. This, Stephenson again suggested,
was essentially a null result—the sun was not shrinking on a long-term basis,
its diameter merely oscillating at regular intervals of about 80 years.

But this is not ‘essentially a null result’. More precisely
worded, Stephenson’s conclusion should have been that the sun’s diameter
is decreasing at a rate somewhere between 0.02 and 0.30 seconds of arc per century,
a rate not incompatible with Gilliland’s suggested almost 0.2 second
of arc per century. Even a rate of 0.02 second of arc per century amounts to a shrinkage
of 15 km (more than nine miles) per century—hardly a near null result! Such
reporting is not completely honest, and only confusing at best.

Only a year later (1983), Stephenson’s colleague, Parkinson, reported on his
measurements made during the total solar eclipse of 1981 and claimed that together
with a reanalysis of previous eclipse and Mercury transit measurements, the data
confirmed that there is no evidence for any long-term change in the solar diameter,
only increased support for an approximate 80 year cyclic variation.9 Because of the considerable accuracy in the reported
observations and measurements of the 1929 eclipse, Parkinson concluded that therefore
it appears that in 1924–25 the radius of the sun was approximately 0.5 second
of arc larger than its average value, and equated this with a maximum in the approximate
80-year variation cycle that he and his colleagues had earlier deduced from the
Mercury transit observations.

Independent confirmation of this conclusion came but two pages later in the same
issue of Nature where Sofia et al. presented their fresh analysis
of the numerous reports on the 1925 and 1979 solar eclipses.10 From different locations, observers had reported on
the duration of the totality during the solar eclipses, and from this data Sofia
and his colleagues found that the solar radius in 1925 was 0.5 second of arc or
375 kilometres (233 miles) larger than in 1979. And they also reported that although
they had shown the solar radius decreased by 0.5 second of arc between 1925 and
1979, the sun’s size in 1925 was not significantly different from that in
1715. Thus they concluded that the solar radius changes are not a simple long-term
uniform trend. They went on to claim that this is consistent with the null result
(no shrinkage) from the transit of Mercury measurements which they claimed were
less accurate than the eclipse results. Like Stephenson and Parkinson, they ignored
the criticisms of Gilliland and his careful reanalysis of all the data sets, to
claim that the Mercury transit data convincingly disproved the existence of a large
long-term uniform decrease of the solar radius.

Whom does one believe?

This of course raises the question as to which scientist or scientists one should
believe? Similarly, whose mathematical analysis of the historical data should be
believed? All the solar astronomers whose work we have cited have impeccable credentials.
Their choice of mathematical manipulations of the observational data vary according
to preference, yet they each promote their own conclusions with equal conviction.
The layperson is left wandering in a maze and wondering how he can resolve the apparently
conflicting evidence to arrive at the truth. While the debate continues to this
day, a clearer picture is gradually emerging, one that still challenges the evolutionists’
multi-billion year age for the sun and solar system. This will be the subject of
our third and final part of the series (published in Creation 11(3):40–43,
June–August 1989).

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